Silica is, as is generally known, added as a filler into rubber compositions for treads to reduce the rolling resistance (to improve the fuel economy) of tires. The use of silica in a rubber composition for treads enables to not only reduce rolling resistance but also enhance wet traction performance.
In order to meet the recent demand for further reduction in rolling resistance, the use of silica is being considered, not only for rubber compositions for treads but also for rubber compositions for other components such as a clinch apex. Unlike rubber compositions for treads, however, conventional rubber compositions for clinch apexes contain carbon black with a large particle size. The use of silica instead of carbon black is not so effective in reducing rolling resistance. Moreover, Patent Literature 1 proposes a method in which a silica having a small nitrogen adsorption specific surface area is used. Unfortunately, this method does not satisfy the recent demand for reduced rolling resistance.
Furthermore, as rubber compositions for automobile tires also need to be excellent in abrasion resistance and processability, a technique is desired which achieves balanced improvements in these properties as well as fuel economy at high levels.